Field Names Don't Match in Leads Form

Field Names Don't Match in Leads Form

In the Fields List the field is named "Last Name" (Screenshot 1: attached). In the Leads Layout it is also named "Last Name" (Screenshot 2: attached), however in the final leads form after the info has been entered and saved as a new lead, the "Last Name" field is now appearing as "Lead Name" (Screenshot 3: attached). This has caused some confusion amongst our sales team. 

Can you help rectify this? The "Last Name" field is not editable in the fields list so I'm not sure why it's converting to "Lead Name" after the information is saved. When a new Lead is created the field appears normally, as "Last Name" but only changes to "Lead Name" when the final info is displayed.